Reversible air propeller



E -rah, w, 1925.,

P. JARAY REVERSIBLE AIR PROPELLEIR Filed June 28, 1920 Patented Feb. 10, 1925.

I 1,525,546 PATENT oFFic's.

PAUL JARAY, FRIEDRIQHSHAFEN, GERMANY, ASSIGNOR TO THE FIRM IIUFT- SCHIFFBAU ZEPPELIN GESELLSCHAFT MIT BESCHRKNKTER HAFTUNG, OF FRIED- RICHSHAFEN, GERMANY.

ItIElV'ERSIIBIiE AIR PBOPELLER.

To all whom it may aoncema I Be it known that I, PAUL JARAY, a citizen of the Austrian Republic, residing at Friedrichshafen a/B., Germany, have invented certain new and' useful Improve- "ments in Reversible Air Propellers, of

which the following is a specification.

. My invention refers to propellers for aerial vehicles and its-particular object is to provide means for reversing the propeller in a simple and yet effective manner,

the efiiciency of the propeller being the same before and after reversal.

As is well known to those skilled in the art, it is necessary to reverse the propeller i. -e. to make it act in an o posite direction whenever an airship or a dying machine is about to land inasmuch as -these vehicles, provided that the propeller be merely brought toa standstill, will, owing to their own momentum and the low resistances en countered, persist for-a while in their for ward movement.

Now by merely changing the direction of rotation of the propellershaft the efi'ective output of the propeller, which latter is now rotating backwards, becomes very low inasmuch as the suction side is then required to act as pressure side and vice versa. It is not possible either to improve this low efficiency by employing propellers having adjustable blades allowing to be gradually set between comparatively low angular limits. For small gradual angular variations of this kind will prove useful only in case that the direction of travel remains substantiallythe same, provided the density of the air, the gradient and the velocity, respectively, be varied ther with.

In the propeller according to the resent invention, now, instead of gradual y set ting the propeller blades, provision is made that the front and rear faces of the blades means for adjusting its blades in two ter together with the inlet and outlet edges will assume their correct posit-ions even after the direction of rotation has changed.

This is effected by reversing in a well known manner the propeller shaft and at the'same time also causing the blades to turn about 180 around their longitudinal axis until they have reached the opposite a position. Thus the propeller according to the present invention is provided with minal positions, each one, thatthe propeller shaft be caused .to rotate ina corresponding sense, resulting in the correct position'of the inlet and outlet edges for,

going ahead and astern, respectively.

In the drawings affixed to this specificar tion and forming part thereof the preferred form of a reversible propeller is illustrated by way of example.- In the drawings- Figs. 1 and 2 are a longitudinal and a cross section, respectively, of the central portion of the propeller and hub.

A is the propeller shaft and B is a hub casing afiixed thereto. C is a bush r0tatably disposed within said hub and'embracing the propeller D which is secured there-- in against rotation by lateral faces d and screwbolts E. Shoulders b on the bush C prevent this latter fromsbeing displaced in anaxial direction. G is a worm rim formed on the bush C and G is a worm disposed on a'shaft located in the hub and carrying a chain wheel F.

Whenever it is desired to reverse the propeller, the propeller shaft is caused to rotate inan opposite direction. At the same time chain wheel F is caused'to rotate from a distance and the bush C and propeller D are thereby carried into the opposite position where the inlet and outlet edges again assume their correct position with relation to the changed directions of rotation, the propeller thereby working with fullv efliciency.

Although I have represented the pro e1- ler as being made in one iece, as usu I wish it to be understood t at my invention may just as well be applied to pro ellers having separate blades jointed toget er by means of a common hub. In such a case the reversing mechanism will again be connected with the hub. As the propeller is reversed for full 180, there is no hindrance to its blades being rigidly interconnected by ing two blades rigidly connected in relation 7 to each other, apropeller shaft, a hub casing fixed to said shaft, a bush embracing the middle portion of said propeller, means for rigidly securing said propeller in relation to said bush, a bearing in said hub oasing for rotatably supporting said bush together with said propeller, and means for turning said bush together with said propeller 180 degrees around their common longitudinal axis.

2. In combination, a propeller comprising two blades rigidly connected in relation to each other, a propeller shaft, a hub casing fixed to said shaft, a bush embracing the' middle portion of said propeller, means for rigidly securlng said propeller in relation tosaid bush, a bearing in said hub casing for rotatably supporting said bush together with said propeller, a worm rim on said bush, a worm mounted in said hub casing and engaging with said Worm rim, an means for operating said Worm adapted for turning said bush together with said propeller 180 degrees around their common longitudinal axis.

ture.

In testimony whereof I a-fiix my signa- 

